The ISO’s proposal would treat fuel secure generators as price takers in the region’s next capacity market auction, not allowing them to set clearing prices. The grid operator and stakeholders would then work to design new market rules for generators that have firm, uninterruptible fuel supplies in future auctions.

The ISO’s filing rejects two changes proposed by FERC in July, saying they would result in capacity overprocurement. The proposed changes are separate from a cost recovery proposal filed by Exelon for its Mystic gas plant, both of which must be approved by the federal regulatory body.

Squeezed by tight filing deadlines and an upcoming auction, ISO-NE on Friday proposed a bridge to transition its market into valuing fuel security.

In July, FERC ordered the ISO to reshape its market rules within 60 days to better compensate generators that keep fuel like oil or liquefied natural gas onsite. Federal regulators recommended two changes — devising a fuel security payment in capacity markets, or taking the fuel secure generators out of the market altogether.

The ISO on Friday rejected both those proposals. Allowing plants like Mystic to operate outside the capacity market would allow other generators to take their capacity supply obligations, the ISO said, leading to more plants on the system and suppressed wholesale prices.

Devising a fuel security payment in the capacity market could be a viable option, ISO-NE said, but the grid operator has not had enough time to design such a mechanism for its next auction in May 2019.

Instead, the ISO proposes to treat those fuel secure resources as “price takers” for that auction. In that case, generators like the Mystic plant could receive market revenues, but not set auction prices for other resources.